This invention relates generally to a zoom lens barrel capable of axial zooming operation, and more particularly to such a zoom lens barrel which includes an operating ring to be rotated and axially moved for focusing and zooming, respectively, and which has incorporated a zoom lens optical system with a first lens group used for both focusing and zooming.
In a zoom lens barrel capable of axial zooming operation, a scale ring is generally provided so that it may only be rotated and moved along the optical axis by the respective rotation and movement of an operating ring along such axis. The end of the scale ring along the optical axis indicates a focal distance scale formed axially on a stationary barrel, and an index formed on the stationary barrel indicates a camera-to-subject distance scale formed circumferentially on the scale ring.
However, such a scale ring is not required for the zooming and focusing operations so that, when provided, it effects an increase in the number of parts, processes, and assembly operations required for the zoom lens barrel. Accordingly, prior art zoom lens barrels of the above-mentioned type are costly to produce and are disadvantageous in that they are relatively large in size and heavy in weight.